A comparison of the refractory periods induced by hypertonic airway challenge and exercise in bronchial asthma

We have compared the changes in FEV1 of 10 asthmatic patients who were subjected in random order to paired challenges with different combinations of exercise and aerosolized hypertonic 3.6% saline. The challenges were separated by 60 min when the FEV1 values had returned to within 10% of baseline values. Four patients were refractory to exercise-induced asthma (EIA) after an initial exercise task, and these patients also demonstrated a refractory period to hypertonic-saline-induced bronchoconstriction after an initial hypertonic challenge. Furthermore, hypertonic challenge produced refractoriness to EIA in the patients, and exercise rendered them refractory to hypertonic-saline-induced asthma. Six subjects were not refractory to EIA after an initial exercise task, and they were also not rendered refractory by an initial hypertonic challenge to asthma induced by hypertonic saline or by exercise. Histamine-induced bronchoconstriction in the 4 refractory subjects did not induce a refractory period to EIA, indicating that the refractory periods developing after hypertonic saline challenge and exercise were not due to the bronchoconstriction alone. Inhalation of isotonic saline in the same volumes as those used for hypertonic challenges did not induce a refractory period, indicating that the refractory period caused by the inhalation of hypertonic saline was not due to the volumes of fluid inhaled. Thus, exercise and aerosolized hypertonic saline induced refractoriness interchangeably, suggesting that airway hypertonicity and exercise produced a refractory period through a very similar, if not identical, final common pathway.